Heat the olive oil and butter in a heavy pot on medium heat.

Saute the onion, garlic, carrots, celery, salt, and pepper for 5 minutes.

Add the pancetta and saute until the fat is rendered, about 2-3 minutes.

Add the ground beef, nutmeg and using a wooden spoon break up the meat.

Continue to cook until the meat is browned.

Add the milk and bring to a slow boil.

Continue to cook until the milk is mostly evaporated.

Add the tomatoes and stir.

Bring the mixture to a boil, then reduce the heat to a very low simmer.

Cook uncovered for 3-4 hours, stirring occasionally.

Taste and adjust salt along the way.

If the sauce begins to dry out, add a little water to maintain desired consistency. Be sure that the heat is low.